RALEIGH, N.C. — Four people were arrested Tuesday morning as they protested outside a downtown Raleigh building where the state commission responsible for developing regulations that would allow for expanded natural gas drilling in North Carolina was meeting.

The Mining and Energy Commission is scheduled to hold meetings through Wednesday as it tries to meet a 2014 deadline to draft rules for drilling, including the controversial process of hydraulic fracturing, or "fracking." The process involves horizontal drilling through underground shale deposits and injecting a high-pressure mix of water and chemicals into the well to break apart the rock and release trapped natural gas.

Drilling opponents say fracking will contaminate North Carolina's underground water supplies and would compete with other water uses during droughts.

The commission discussed water use, as well as issues such as managing waste and environmental standards, on Tuesday morning. Each fracking well requires 2 million to 5 million gallons of water, and commission members debated whether salt water or recycled wastewater could be used.

A report to the panel said there are no saltwater reserves in the areas where most drilling would occur.

"That's a bit of a pity, but we will not give up. We will look for alternative water, like municipal water and so forth, to take the burden off freshwater withdrawals," said Vikram Rao, chairman of the commission's Water and Waste Management Committee.

Meanwhile, two members of the radical environmental group Earth First! padlocked themselves to the doors of the Archdale Building while the commission was inside. Police were trying to determine how to cut the U-shaped bicycle locks they used when the protesters handed over the keys to the locks, saying they had made their point.

Tamara Matheson and Vincent Michael Gonzalez were charged with disorderly conduct in a public building.

"We are not going to let profiteers exploit and endanger our land and our loved ones," Earth First! member Maria Rowan said. "This hydraulic fracturing has never been done safely. There's been contaminated water. There's been exploding pipelines."

Two other protesters were arrested after they displayed a banner, and police threatened to arrest others if they tried to wave flags, beat drums or chant because the group didn't have a protest permit. Celtia Oakley and Michael Bandes were charged with disorderly conduct and resisting a public officer.

Wednesday's meeting will include a public comment period for 10 speakers, each of whom will get three minutes to describe their thoughts about fracking.